The present invention relates to processors for chipping and shredding vegetation and, in particular, to machines having cutters mounted on a rotor.
Known chippers have employed a relatively heavy, steel disk mounted in a cylindrical housing. The disk has slots where cutting blades are mounted. The. disk housing has a hopper for feeding branches and limbs through the side of a housing and into the spinning cutter blades. A cutter bed bar can be mounted in the cylindrical housing to subjacently support the lower edge of the hopper opening and provide a firm platform to hold the material against the action of the cutter blades. These known chippers can be driven by a gasoline engine or by a drive shaft adapted to be connected to the drive train of a tractor or other machine.
Chippers are normally designed to handle wood of a rated diameter. In some designs, the rating is determined by the material strength of the cutter blades and its supporting structure. Wood larger than the rating can produce excessive stress that may tend to permanently deform or break the chipper or cause excessive wear.
In some embodiments, the limitation on the diameter of wood that the chipper can handle is established by employing a drive shaft having shear bolts. Such drive shafts can be connected to a power source in a tractor or other mechanism. To ensure that excessive power is not applied to the chipper rotor, the drive shaft will disconnect when the shear bolt fractures under excessive load.
In other embodiments, the rating of the chipper is determined by the angular momentum stored in the chipper rotor. Such designs anticipate spinning a relatively heavy rotor at a high speed. Consequently, wood fed into the chipper blades would tend to slow the rotor but not unacceptably so if the wood is of a rated size. Since limbs and other material normally fed into a chipper tend to have a typical length to diameter ratio, manufacturers normally specify a diameter rating, which assumes a typical length. Therefore, a typical limb having a rated diameter (and therefore a typical rated length) can be fed into the chipper rotor without unacceptably reducing its speed and operating efficiency. If wood beyond the rating is fed into chippers of this type, the rotor will slow unacceptably or even stop.
An advantage with this type of design is the fact that the motor or drive shaft spinning the chipper rotor need not have the horsepower needed to supply all of the power required when the chipping is actually occurring. Instead, the motor can store kinetic energy in the rotor using a flywheel effect, so that energy can be withdrawn quickly during chipping without excessively loading the motor.
A conventional shredder can employ a plurality of coaxial disks mounted inside a cylindrical housing. Swinging bars or flails can be mounted between the coaxial disks to articulate and assist in the shredding process. While material to be chipped is brought to the side of a rotating disk, material to be shred conventionally is fed radially into the spaces between the rotating disks.
Chippers and shredders are often used by landscapers, farmers, foresters or others who must reduce various types of materials. For this reason, combined chipper/shredders have been designed. Such combined chipper/shredders have employed two hoppers, one to feed shreddable material radially between coaxial disks and another hopper to feed chippable material to the side of an outer disk carrying chipper blades. A disadvantage with this type of machine is the relative complexity and additional parts needed to accomplish the feeding of different materials along different paths. Also, these structures have required a relatively large number of flails to accomplish the shredding. Moreover, these machines have been relatively inefficient and needed 20 outlet screens to keep partially disintegrated material cycling within the housing before being disintegrated enough to pass through the holes of the screen.
Known shredders have included a vacuum hose that can be connected to the shredder hopper. Consequently, the vacuum hose can be brought to the debris, which is then sucked into the shredder.
U.S. Pat. No. 3,276,700 shows a wood chipper employing a rotary disk with angularly spaced knives and passageways. Material is fed to one side of the disk and chips pass through the other side while air is continuously circulated throughout the housing.
U.S. Pat. No. 3,756,517 shows a forage blower with a recutter. Material is transferred from the cutter to the impeller in the direction of rotation of the impeller. Therefore, the exit velocity of the material has a significant component towards the discharge opening. This assembly includes a perforated cylindrical screen or cage. Material passing through the cage is thrown into impeller paddles which sweep the recut materials into an outlet. See also U.S. Pat. Nos. 2,361,278; 3,276,700; 3,917,176; 4,951,882.